The S&P 500 kept its streak alive for a seventh straight week. That’s the longest stretch of advances in more than two years. Investors piled into stocks at the beginning of the year after Congress reached a deal to avoid the fiscal cliff. The gains continued as investors were encouraged by signs that housing and jobs are recovering. Earnings have also held up well. But there are signs the rally is running out of steam. The Dow ended the week down, falling for the second week. Walmart was the biggest decliner in the index Friday. Shares fell after Bloomberg News published parts of an internal e-mail that said February sales were a ‘total disaster.’